In a panel display system including a display panel, data associated with respective subpixels of respective pixels of the display panel are transmitted to a display driver which drives the display panel. Such data may include, for example, image data specifying the grayscale values of the respective subpixels of the respective pixels and correction data associated with the respective subpixels of the respective pixels. The correction data referred herein is data used in a correction calculation of image data to improve the image quality. Recently, the number of pixels of a display panel to be driven by a display driver is increased, and this causes an increase in the amount of data to be supplied to the display driver. The increase in the data to be supplied to a display driver may cause increases in the baud rate and power consumption which are required for the data transfer to the display driver.
One approach to address the increase of data to be supplied to a display driver is to generate compressed data by performing data compression on original data to be transmitted to the display drier, and to supply the compressed data to the display driver. In this case, decompressed data corresponding to the original data is generated by decompressing the compressed data in the display driver and the display driver is operated in response to the decompressed data. This operation allows supplying an increased amount of data to a display driver in a short period of time.
In a panel display system configured to transmit compressed data to a display driver, however, restrictions of hardware of the display driver may cause an issue. First of all, a display driver, which handles an increased amount of compressed data, is required to rapidly decompress the compressed data. When the compressed data is decompressed with a hardware circuit in the display driver, on the other hand, there is a limitation in the allowed amount of compressed data for which decompression processing is performed in each clock cycle. This is because a high breakdown voltage process is used to manufacture a display driver to achieve high-voltage operation. In general, the operation speed of a device manufactured with a high breakdown voltage process is not so high. This may become a restriction against rapidly decompressing compressed data in a display driver.
This problem is especially significant when variable length compression is used in the data compression. When a compressed data compressed through a variable length compression is decompressed, a bit search is perform to identify the end of each code and the value of each code; however, a display driver suffers from a limitation of the number of bits for which the bit search can be performed in each clock cycle. This may become a restriction against rapidly decompressing the compressed data generated through a variable length compression. The limitation of the number of bits for which the bit search can be performed is significant especially when a long code length is allowed in the variable length compression.
Accordingly, there is a technical need for rapidly decompressing compressed data in a display driver in a panel display system configured to transmit compressed data to a display driver.
It should be noted that Japanese Patent Application Publication No. 2011-150536 discloses a technique for achieving variable-length coding (run-length coding and Huffman coding) through parallel processing by using a reconfigurable circuit.
Japanese Patent Application Publication No. H06-237448 discloses a coding apparatus which performs coding of quantization/DCT coefficients by using two-dimension Huffman table reference sections provided in parallel and a technique for decoding an image coded by the coding apparatus by using two-dimension Huffman table reference sections provided in parallel.
Japanese Patent Application Publication No. H04-177916 discloses an image data coding circuit which performs coding of still picture data using a DCT circuit, a quantization circuit, a differential circuit, a run-length coding circuit and a Huffman coding circuit.
Japanese Patent Application Publication No. 2007-279290 discloses a display device which displays an image through controlling a display of each pixel in response to an image data associated with each pixel. The display device includes a correction memory storing data for correcting variations in the brightness of the respective pixels and a correcting means which performs correction of brightness mura by performing an operation on input data with the data stored in the correction memory, and the display device is configured to store correction data generated through entropy coding in the correction memory and perform the operation on the input data while decompressing the data in the correcting means. Huffman coding is used as the entropy coding and the correction memory has different Huffman tables for the respective sub-areas.